The token is a Zombie in addition to its other types and is black instead of its other colors. Its base power and toughness are 4/4. It has no mana cost, and thus its mana value is 0. These are copiable values of the token that other effects may copy.

If a creature card with eternalize is put into your graveyard during your main phase, you'll have priority immediately afterward. You can activate its eternalize ability before any player can try to exile it.

Once you've activated an eternalize ability, the card is immediately exiled. Opponents can't try to stop the ability by exiling the card.

The token copies exactly what was printed on the original card and nothing else, except the characteristics specifically modified by eternalize. It doesn't copy any information about the object the card was before it was put into your graveyard.